Respiratory Syncytial Virus (RSV) is the most common cause of severe lower respiratory tract infections (LRTI) in young infants, virtually all of whom suffer at least one RSV infection in the upper respiratory tract by the age of two. In very young infants, infection can progress to the lower respiratory tract causing bronchiolitis and pneumonia that may necessitate hospitalization.
RSV is an enveloped virus with a negative strand non-segmented RNA genome. It belongs to the Mononegavirales order, Paramyxoviridae family and Pneumovirus genus. RSV exhibits nucleocapsid-associated RNA dependent RNA polymerase (RdRp) activity for viral transcription and replication, which occurs in the cytoplasm of an infected cell.
The RSV polymerase is comprised of at least five viral components: the genomic RNA, and the L, N, P and M2-1 proteins. Together these components form a Ribonucleoprotein (RNP) complex with RdRp activity required for the synthesis of both viral genomic RNA (“replicase” activity) and sub-genomic mRNAs (“transcriptase” activity). As opposed to the replication of viral products, RSV mRNAs are co-transcriptionally capped (i.e. guanylated and methylated) at their 5′ ends and polyadenylated at their 3′ ends by the RNP complex. These modifications are necessary for translation of the viral mRNAs by the host protein synthesis machinery. The RNP complex functions exclusively in the cytoplasm of the RSV-infected cells. Since the host proteins responsible for capping of mRNAs are located in the nucleus of the cell, capping of its mRNAs by the viral RNP complex is essential for the synthesis of RSV proteins. Thus, the RSV RNP complex is an attractive target in screening for potential antiviral therapeutics since it has multiple activities essential for viral replication.
U.S. Pat. No. 4,176,184 discloses 7,7-dimethyl-2-(2-methoxyphenyl)-5-[3-(2-(3,4-dimethoxyphenyl)ethylamino)propyl]-5H,7H-imidazo[4,5-h]isoquinoline-4,6-dione dihydrochloride (example 28) having anti-arrhythmic activity.
The present invention therefore provides novel compounds, compositions, uses and methods that inhibit Respiratory Syncytial Virus polymerase essential for viral replication.